1. Field of the Invention
The present invention relates to a passive safety system including a passive safety device and a control device operating controllably the passive safety device. Especially, the present invention relates to a passive safety system having features of determining whether impacts at the time of collision necessitate an operation of the passive safety device or not, and controlling the operation of the passive safety device based on the determined result.
2. Description of the Prior Art
FIG. 1 is a plan view showing a front section of a vehicle (automobile) including a conventional passive safety system. In the drawing, a reference numeral 1 denotes a vehicle, 2 denotes an airbag acting as a passive safety device arranged at a front of seats mounted on the vehicle 1, and 3 denotes a passive safety control means developing the airbag 2. The passive safety control means 3 includes an acceleration sensor (not shown) and a microcomputer (not shown) receiving input an acceleration detection signal from the acceleration sensor as a digital signal.
An operation will be hereafter explained.
When the vehicle 1 undergoes an impact of a head-on collision, the acceleration sensor mounted in the interior of the passive safety control means 3 detects the acceleration caused by an impact at the time of collision to output with respect to the acceleration detection signal to the microcomputer. The microcomputer performs an operation based on the acceleration detection signal inputted from the acceleration sensor to determine whether the airbag 2 should be developed or not. With the determination, deceleration of the vehicle becomes important. The passive safety control means 3 integrates the impact acceleration detection value obtained from input signals inputted from the acceleration sensor with respect to time, and calculates the deceleration. An offset component due to noise with respect to the input signals however superimposes on the deceleration in practical, and the integrated value of the impact acceleration is accumulated due to the offset component in normal driving.
With the conventional passive safety system constituted as described above, it takes measures to reset the integrated value under a given condition to prevent the accumulation of the integrated value of the impact acceleration in normal driving. In this case, since it is however difficult to reset in good timing, a reset process means for resetting the integrated value in good timing must be newly added to the existing constitution.
Another conventional passive safety system uses a method including the steps of setting a required subtraction value, performing a subtraction from an input value inputted from the acceleration sensor always, and then modifying the integrated acceleration value to zero when the integrated acceleration value is zero or less. Since a ratio subtracted when a low-impact is inputted over a long time is however different from a ratio when a high-impact is inputted over a short time, it is difficult to calculate a precise integrated value.
Accordingly, it is an object of the invention to provide a passive safety system calculating precisely a deceleration caused by an impact at the time of collision and calculating precisely a deceleration without accumulating the acceleration integral without adding a major processing to the existing constitution in normal driving.
It is an object of the invention to provide a passive safety system determining precisely whether the integrated acceleration value at the time of collision is or not a value which necessitate an operation of the passive safety device.
It is an object of the invention to provide a passive safety system calculating precisely the integrated acceleration value using a simple method without dividing a calculation of the integrated acceleration value into an accelerated direction and a decelerated direction.
It is an object of the invention to provide a passive safety system further rapidly distinguishing a collision from a driving over a rough road.
It is an object of the invention to provide a passive safety system calculating precisely the deceleration at the time of collision by postponing a reset process of the integrated acceleration value when the physical quantity provisionally enters within a reference value range due to a vibration component of collision.
In order to achieve the object of the present invention, a passive safety control means of the passive safety system computes a physical quantity based on the impact acceleration detection signal inputted from the acceleration sensor, and sets maximum and minimum reference values of the physical quantity in normal driving. The passive safety control means then performs a computation with respect to addition of a present acceleration inputted from the acceleration sensor to an integrated acceleration value at this point in time when the physical quantity crosses a range defined between the maximum and minimum reference values. Alternatively, the passive safety control means performs a computation with respect to a reset process of the integrated acceleration value when the physical quantity remains within the range defined between the maximum and minimum reference values. In this way, it is possible to keep the integrated acceleration value in normal driving to zero and to calculate precisely the deceleration of collision.
The passive safety control means may output an operational signal operating the passive safety device when an integrated reference value of the integrated acceleration value computed based on the impact acceleration detection signal inputted from the acceleration sensor. In this way, it is possible to operate the passive safety device without any error.
The passive safety control means may have a high-frequency attenuation means attenuating a high-frequency with respect to an impact signal inputted from the acceleration sensor, the impact signal being a physical quantity operated on the basis of the impact acceleration detection signal inputted from the acceleration sensor, the high-frequency attenuation means including a high-frequency breaking circuit and a sectional balancing process means; and a feature of processing an operational result passed through the high-frequency attenuation means as an input value. In this way, it is possible to determine whether a collision necessitates an operation of the passive safety device or not, with stability without respect to a high-frequency noise.
The passive safety control means may include a filter means extracting a frequency component being a physical quantity operated on the basis of the impact acceleration detection signal inputted from the acceleration sensor, which is peculiar to a collision of the vehicle from the acceleration signal inputted from the acceleration sensor; and a feature of processing an operational result passed through the filter means as an input value. In this way, it is possible to distinguish a normal state with stability from a collision state.
The passive safety control means of the passive safety system may have features of dividing a physical quantity operated on the basis of the impact acceleration detection signal inputted from the acceleration sensor into the negative and positive components, setting a required weighted scaling with respect to the negative and positive components, and processing a multiplication result due to the weighted scaling as an input value. In this way, it is possible to prevent integral of the acceleration with respect to a vibration wave caused on a driving of a rough road. Inversely, when the weights are performed to input a value resulting from multiplying an attenuation directional component by a required scaling, the integrated acceleration value becomes small with respect to the attenuation directional component caused at the time of collision. The weights of the attenuation directional component are therefore different from those of the acceleration directional component, and it is possible to result in the collision being rapidly distinguished from the driving over the rough road.
The passive safety control means of the passive safety system has features of computing a physical quantity based on the impact acceleration detection signal inputted from the acceleration sensor, setting maximum and minimum reference values of the physical quantity in normal driving, performing a computation with respect to addition of a present acceleration inputted from the acceleration sensor to the physical quantity when the physical quantity crosses a range defined between the maximum and minimum reference values, setting a function of operating a subtraction value or an addition value with respect to the present integrated acceleration value when the physical quantity remains within the range defined between the maximum and minimum reference values, and performing a subtraction or an addition of the integrated acceleration value based on the function to modify a reset period of the integrated acceleration value. In this way, it is possible to shorten a reset time of the integrated acceleration value.
The passive safety control means of the passive safety system computes a physical quantity based on the impact acceleration detection signal inputted from the acceleration sensor, and sets maximum and minimum reference values of the physical quantity in normal driving. The passive safety control means then performs a subtraction of an integrated acceleration value when the integrated acceleration value at the time the physical quantity crosses a range defined between the maximum and minimum reference values is positive. Alternatively, the passive safety control means performs an addition of the integrated acceleration value when the integrated acceleration value at the time the physical quantity remains within the range defined between the maximum and minimum reference value is negative. It is therefore possible to monitor the integrated acceleration value at the present time. When the integrated acceleration value is positive, a subtraction of required value can be performed. When the integrated acceleration value is negative, an addition of required value can be performed. In this way, it is possible to perform a reset process so as to converge the integrated acceleration value in normal driving to zero at all times, and prevent the accumulation due to a superimposing of the noise component. It is therefore possible to calculate precisely the integrated acceleration value using a simple method without dividing a calculation of the integrated acceleration value into an accelerated direction and a decelerated direction.
The acceleration sensor may be set to detect the acceleration in a longitudinal direction of the vehicle. In this case, when any one of front and rear sides is defined as the positive component of the acceleration sensor, the other side is defined as the negative component of the acceleration sensor, the passive safety control means may have features of operating controllably the passive safety device arranged at a positive component side when the integrated acceleration value based on the acceleration detection signal inputted from the acceleration sensor exceeds a reference value of the integrated acceleration value set as the positive component, and operating controllably the passive safety device arranged at a negative component side when the integrated acceleration value based on the acceleration detection signal inputted from the acceleration sensor does not attain a reference value of the integrated acceleration value set as the negative component. In this way, it is possible to determine a collision in both of front and rear collisions due to the same logic, and operate controllably the passive safety device without any error.
The acceleration sensor may be set to detect the acceleration in a lateral direction of the vehicle. In this case, when any one of right and left sides is defined as the positive component of the acceleration sensor, the other side is defined as the negative component of the acceleration sensor, the passive safety control means may have features of operating controllably the passive safety device arranged at a positive component side when the integrated acceleration value based on the acceleration detection signal inputted from the acceleration sensor exceeds a reference value of the integrated acceleration value set as the positive component, and operating controllably the passive safety device arranged at a negative component side when the integrated acceleration value based on the acceleration detection signal inputted from the acceleration sensor does not attain a reference value of the integrated acceleration value set as the negative component. In this way, when a collision is caused in the lateral direction of the vehicle, it is possible to control both of the passive safety devices at the same time.
The passive safety control means of the passive safety system may have features of computing a physical quantity based on the impact acceleration detection signal inputted from the acceleration sensor, setting maximum and minimum reference values of the physical quantity in normal driving, performing a computation with respect to addition of a present acceleration inputted from the acceleration sensor to an integrated acceleration value at this point in time when the physical quantity crosses a range defined between the maximum and minimum reference values, measuring a period of time after the physical quantity exceeds the range, and postponing a reset process of the integrated acceleration value when the measured time period is shorter than a required period. In this way, it is possible to postpone a reset process of the integrated acceleration value when the physical quantity provisionally enters within a reference value range due to a vibration component of collision, and calculate further precisely the deceleration at the time of collision.